Heat exchanger construction



June. 27, 1961 P. s. OTTEN HEAT EXCHANGER CONSTRUCTION 3 Sheets-Sheet 1 Filed Jan. 28, 1957 INVENTOR. Philip S. Owen 9 W? ATTORNEYS June 27, 1961 P. s. OTTEN 2,990,162

HEAT EXCHANGER CONSTRUCTION Filed Jan. 28, 1957 5 Sheets-Sheet 2 IN V EN TOR.

BY QWX ATTORNEYS June 27, 1961 P. s. OTTEN 2,990,162

HEAT EXCHANGER CONSTRUCTION Filed Jan. 28, 1957 3 Sheets-Sheet 3 IN V EN TOR.

Philip 8. 0m

BY 9W2 ATTORNEYS Unite Filed Jan. 28, 1957, Ser. No. 636,577 6 Claims. (Cl. 257-235) The invention relates to heat exchangers, and more particularly to a device for heating low-temperature fluids or liquids with relatively high-temperature gases.

The construction and operation of jet-propelled devices requires the provision of a heat exchanger for heating low-temperature liquids, such as liquid with available relatively high-temperature gases. The design and construction of such heat exchangers involves a number of complicating factors.

First, the heat exchanger must be small in size, light in weight, resistant to the attack of high-temperature gases, and adapted for withstanding extreme thermal shock without damage.

Second, the operation of such heat exchangers must permit the flow of a large volume of high-temperature gas through the heat exchanger with minimum pressure loss. That is, the high temperature heating gases must flow through the heat exchanger in a direct path without changes or angular turns in the direction of flow and with a minimum obstruction to gas flow by the tubes heated thereby through which the medium to be heated flows.

Third, consistent with the stated requirements, the heat exchanger must provide a maximum of tube surface within a small shell volume, along with minimum obstruction to gas flow incident to the tube-header connections and the inlet and outlet connections to the headers.

Fourth, the heat exchanger construction must be such as to be easily manufactured as a self-contained unit with safe and effective fluid-tight joints, preferably welded, between the shell and headers and heating gas inlet and outlet connections, and between the tubes and headers or manifolds.

Finally, the required heat exchanger construction must be such that with a minimum of design change it can be adapted for separately and simultaneously heating two different liquids or fluids, such as liquid 0 and liquid N No known prior constructions satisfy the indicated requirements. Feed water heaters have long been used which include coiled tubes providing a large amount of heat exchange surface, but such prior constructions have been large in size, very heavy in weight, and are not adapted for utilizing very high-temperature gases as the heating medium in large volumes with a minimum of pressure loss.

Household water heaters installed as attachments in stove or range fines or pipes have been used which include cast metal annular tube headers or manifolds, but such prior constructions do not provide the required amount of tube surface in a light-weight, self-contained shell-tube-header unit capable of being manufactured from corrosion-resistant materials which can withstand extreme thermal shock and can be provided with welded joints, which may be inspected, between the various components of the self-contained unit.

Accordingly, it is a general object of the present in-.

vention to provide a new heat exchanger construction for heating low-temperature liquids, such as liquid 0 which may have a temperature of -200 F. to 300 F. with high-temperature gases which may have a temperature of tates Patent ice shock incident to heating liquids at temperatures of from -200 F. to --300 F. with heating gases having a temperature up to 1500 F.

Also, it is an object of the present invention to provide a new high-temperature heat exchanger construction for heating low-temperature liquids with high-temperature gases which permits a large volume of generally unidirectional gas flow through the heat exchanger with a minimum of pressure loss.

Also, it is an object of the present invention to provide a new heat exchanger construction incorporating the foregoing arrangements and advantages in which a maximum amount of tube heat transfer surface is provided Within a small-size self-contained unit with a minimum of tube obstruction to the unidirectional gas flow through the heat exchanger.

Moreover, it is an object of the present invention to provide a new heat exchanger construction incorporating the stated features which may be readily manufactured with welded joints between the various components of the self-contained unit.

Also, it is an object of the present invention to provide a new heat exchanger construction incorporating the stated features and arrangements in which provision may be made for separately and simultaneously heating two different low-temperature liquids.

Finally, it is an object of the present invention to provide a new heat exchanger construction which satisfies the existing need in the art, solves the problems indicated, eliminates the difliculties present in the construction and use of prior heat exchanger structures, and obtains the foregoing advantages in an eflicient, effective and simple manner.

These and other objects and advantages, apparent to those skilled in the art from the following description and claims may be obtained, the stated results achieved, and the described difficulties overcome by the structures, combinations, arrangements, subcombinations, parts, and elements which comprise the invention, the nature of which is set forth in the following general statement, preferred embodiments of which-illustrative of the best modes in which applicant has contemplated applying the principles-are set forth in the following description and shown in the drawings, and which are particularly and distinctly pointed out and set forth in the appended claims forming part hereof. I

The nature of the discoveries and improvements of the present invention may be stated in general terms as preferably including in heat exchanger construction, a plurality of spaced toroidal manifolds or headers, a shell connected to and extending between at least two spaced headers forming a tubular shell compartment having an inlet opening defined by the inner periphery of one of the toroidal headers and having an outlet defined by the inner periphery of the other spaced toroidal header, the shell being connected to said two spaced headers preferably by a welded joint at the outer periphery of each of said headers, a plurality of coiled tubes connected to and between said spaced headers and located in nested arrangement within the shell chamber with the axes of the tube coils extending parallel to the coinciding longitudinal axes of the shell and spaced toroidal headers, inlet means connected to at at least one of the headers and extending externally of the shell, outlet means connected to at least one of the headers and extending extemally of the shell, an axially-extending tubular inlet connected with one of the headers, an axially extending tubular outlet connected with another spaced header, the tube connections with the headers being welded joints, and the headers each being formed as half-sections welded together at the maximum and minimum diameter circumferences of the toroidal shape to permit formation of the header-tube joint welds prior to welding the header half-sections together.

By way of example, several embodiments of the improved heat exchanger construction of the present invention are shown in the accompanying drawings forming part hereof wherein:

FIGURE 1 is a diagrammatic side elevation of one form of improved heat exchanger;

FIG. 2 is a longitudinal section through the heat exchanger illustrated in FIG. 1 taken in planes passing through the centers of the various inlet and outlet connections to the headers;

FIG. 3 is a cross-section through the construction illustrated in FIGS. 1 and 2;

FIG. 4 is a longitudinal section through a modified form of improved heat exchanger construction;

FIG. 5 is an end elevation looking toward the left end of FIG. 4;

FIG. 6 is an expanded view of two header half-sections prior to assembly;

7 FIG. 7 is a diagrammatic top view of the lower header half-section illustrated in FIG. 6; and

FIG. 8 is an enlarged fragmentary view of a portion of FIG. 2.

Similar numerals refer to similar parts throughout the various figures of the drawings.

One of the improved heat exchangers is. illustrated generally at 1 in FIGS. 1, 2 and 3 and includes a shell 2, one set of outer spaced toroidal manifolds or headers 3 and 4, a second set of intermediate spaced toroidal headers 5 and 6, and two series of coiled tubes 7 and 7a.

The shell 2 is connected to, and extends between, the spaced headers 3 and 4, and 5 and 6 preferably by being welded to the outer peripheries of the headers 3, 4, 5 and 6 as indicated at 8, 9, 1t) and 11 in FIG. 2. The shell 2 is cylindrical in shape and has the same inner diameter as the maximum outer diameter or periphery of the toroidal headers 3, 4, 5 and 6.

The shell 2 thus forms a tubular shell compartment having an inlet opening defined by the inner periphery of the header 4 and an outlet opening defined by the inner periphery of the header 3.

A tubular inlet member 12 is welded to the inner periphery of the header 4 as indicated at 13, and a tubular outlet member 14 is welded to the inner periphery of the header 3 at 15.

Heating gases may be directed into inlet member 12 from any suitable source, as indicated by the arrows 16, and such gases pass through the shell chamber and out through outlet member 14, as indicated by the arrows 17.

The longitudinal axis of the shell, indicated by the dot-dash line 18 in FIG. 2, coincides with the axes of each toroidal header 3, 4, 5 and 6 so that the heating gases in passing through the heat exchanger 1 generally follow linear paths.

An inlet member 19 is connected to header 3 and com municates with the interior thereof; and an outlet member 20 is connected with the header 4 and communicates with the interior thereof. Another inlet member 21 is connected with the header 5 and communicates with the interior thereof, while an outlet member 22 is connected with the header 6 and communicates with the interior thereof. The inlet and outlet members 13, 20, 21 and 22 each extend through the shell 7, as shown, in being connected with their respective headers; and the connections between the inlet and outlet members 19, 20, 21 and 22 and their respective headers and the shell 7 are preferably formed as welded joints.

A plurality of plate-like spacer members 23 are welded at spaced circumferential intervals extending between the headers 3 and 5; and a similar series of spacer members 24 are connected between the headers 4 and 6. These spacer members 23 and 24 assist in strengthening and maintaining rigidity in the completed unit and maintain the headers 3 and 5 and 4 and 6 properly spaced during 4 assembly of the unit 1. Furthermore, the inherent strength of the toroidal headers 3, 4, 5 and 6 and their connection to the shell 7 interiorly at the end portions of the shell provide a strong and rigid structure permitting the shell 7 and headers 3, 4, 5 and 6 to be formed of relatively light gauge metal.

The series of coiled tubes 7 extend between the headers 5 and 6 as shown in FIGS. 2 and 3. Each coiled tube 7 has an intermediate coiled portion 25, and end portions 26. The coiled tubes 7 are located in nested arrangement within the shell chamber with the axes of the tube coils extending parallel to the coinciding longitudinal axes 18 of the shell and spaced toroidal headers. Referring to FIG. 3, certain of the coiled tubes 7 are arranged with their tube coil axes located on a circle immediately within the shell 2 and another group of coiled tubes 7 is located with their axes extending through a circle of smaller diameter while other groups of coiled tubes 7 are located with their axes passing through a circle of still smaller diameter.

As shown in FIG. 2, the tube ends 26a of certain groups of coiled tubes 7 are bent at an angle for connection with the headers 5 and 6.

Similarly, the series of coiled tubes 7a extend between and are connected to the headers 3 and 4 and include coiled portions 27 and bent tube ends 28 for connection with the headers 3 and 4. For the purpose of illustration, each coiled tube 7 and 7a is represented diagrammatically in FIG. 3 by two concentric circles, and the coiled tubes 7a have cross-hatching between the concentric circles in FIG. 3 to distinguish between the series of coiled tubes 7 and the series of coiled tubes 7a.

The coiled tubes 7a, as shown in FIG. 3, are also located on circles of increasingly smaller diameters with one central coiled tube 7a extending with its tube coil axis coinciding with the heat exchanger axis 18.

I The ends 26 and 28 of the coiled tubes 7 and 7a are each connected by a welded joint with their respective headers 3, 4, 5 and 6. Referring to FIG. 8, wherein the welded header-tube end connections are shown somewhat diagrammatically, the weld is formed between the tube ends and the wall 29 of all of the toroidal headers by welds 30 located within the toroidal headers.

The toroidal headers 3, 4, 5 and 6 are fabricated by separately forming half-sections 31 and 32 as illustrated in FIG. 6. The toroidal half-sections 31 and 32 may be spun from sheet metal rings or discs of the proper gauge; and one of the half-sections, such as half-section 32, may be provided with a series of openings 33 for connection with the tube ends.

During assembly, the ends 26, 26a or 28 of the coiled tubes 7 are connected to the respective toroidal halfsections 32 by welded joints 30 (FIG. 8) which may be formed at locations within the interior of the resulting toroidal headers. This permits ready welding access for forming the welds 30 at the inside or concave surface 34 of an apertured half-section 32, and also permits ready inspection of the welds 30 for any flaws. Furthermore, the formation of the welds 30 on the interior of the resulting toroidal header permits any desired location or spacing of the tube openings 33 without creating difficulties in forming the welds, as would be the case if the welds 30 were formed at the exterior surface of the toroidal headers.

After the various tube ends have been welded to the half-sections 32 of the toroidal headers 5 and 6, the other half-sections 31 of the headers 5 and 6 may be welded to the half-sections 32 at It 11, 35 and 36 (FIG. 2) at the maximum and minimum diameter circumferences of the toroidal shape.

The half-sections 32 of the headers 3 and 4 preferably are first assembled by spacers 23 and 24 with the halfsections 31 of headers 5 and 6. Then the various groups of tubes 7a may have their tube ends welded to the halfsections 32 of the headers 3 and 4. The half-sections 31- 3 of the headers 3 and 4 may then be welded to the half sections 32 thereof by the welded joints 8 and 9 and 13 and 15 at the maximum and minimum diameter circumferences of the toroidal shapes of headers 3 and 4. The welded connections, in assembling the half-sections of the headers 3, 4, and 6, may be formed separately or at the same time that the headers are welded by the indicated joints to the shell 2 and to the tubular inlet members 12 and :14.

Each of the coiled tubes 7 is preferably formed from seamless tubing of the desired gauge and coiled to the desired outside coil diameter with the desired number of convolutions per inch in forming the spiral coil. The average length of uncoiled tube used to form any one of the tube coils 7 is many times the length of any coiled tube from its connection to spaced headers 5 and 6, or 3 and 4. Thus, the average length of any uncoiled tube for any coiled tube 7 or 7a may be six times the length of the coiled tube 7 or 711 between its end connections with headers 5 and 6, or 3 and 4.

All of the parts of the heat exchanger unit 1 are preferably formed of stainless steel or other material resistant to corrosion and having the required strength at high temperature so as to resist damage from the high-temperature gases forming the heating medium passed through the shell.

The heating medium may, for instance, be exhaust gases at a temperature of, say, 1500" F. supplied from a source, not shown, to the exhaust gas inlet member 12. The hot gases then pass in generally unidirectional paths through the shell chamber and through and around the coils of the coiled tubes 7 and 7a, and thence out of the heat exchanger unit through exhaust gas outlet 14, all as indicated by the arrows 16 and 17, in FIG; 2.

Since the inlet and outlet members 12 and 14 have smaller diameters, as shown in FIG. 2, at their inlet and outlet openings 37 and 38, than the minimum diameters of any of the toroidal headers 3, 4, 5 and 6, the headers do not obstruct the gas flow in any manner. The principal obstructions to gas flow through the shell chamber, aside from gas flow along and around the tube coils where heating of the heated medium occurs, are the bent end portions 26a and 28 of certain of the coiled tubes 7 and 7a. This obstruction results from the angled location of the tube ends 26a and 28 with respect to the direction of gas flow.

However, this tube end obstruction to gas flow is minimized by the utilization of coiled tubes, because the number of obstructing bent tube end portions 26a and 28 is a minimum. For instance, if straight, rather than coiled, tubes were used to provide the same amount of tube surface in the heat exchanger, for the example given, six times as many tubes would be required, which, in turn, would provide six times as many bent tube ends obstructing gas flow.

The unit construction illustrated in FIGS. 1, 2 and 3 provides a compartmentized heat exchanger such that, for instance, liquid nitrogen may be admitted through inlet member 19 into inlet header 3 from which it passes through the coiled tubes 7a connected to header 3. The liquid is heated by the counterflow exhaust gases passing through the shell chamber, and nitrogen passes from the unit through outlet member 22. Similarly, liquid oxygen may be introduced separately into the inlet header 5 through inlet member 21 and is heated in passing through coiled tube 7 and may be withdrawn from the heat exchanger through outlet member 22 connected with outlet header 6.

The liquids or fluids to be heated thus may be introduced into the heat exchanger at temperatures of 200 F. to 300 F. This may impart substantial thermal shock to the elements of the unit 1, but the particular construction withstands such thermal shock because the coiled tube arrangement inherently constitutes a free expansion joint for the tubes with relation to theheaders and shell. Y

1 An alternate improved heat exchanger construction is illustrated generally at 39 in FIGS. 4 and 5, similar'in all respects to the heat exchanger 1 of FIGS. 1 and 2, except that it is not compartmentized. The heat exchanger unit 39 includes a shell 40 and one set of spaced toroidal headers 41 and 42 between which a series of coiled tubes 43 extend, the ends 44 of the coiled tubes 43 being connected to the headers 41 and 42.

The header 41 is provided with a header inlet 45 and similarly the header 42 is provided with a header outlet 46. A tubular heating gas inlet member 47 is welded'at 48 to the header 42, while a tubular heating gas outlet member 49 is welded to header 41 at 50, so that heating gases may be directed into the shell as indicated by the arrows 51, and may be exhausted from the shell chamber through outlet 49, as indicated by the arrows 52.

In the form of construction shown in FIGS. 4 and 5, the gas inlet and outlet members 47 and 49 are of larger diameter than the inner diameters of the headers 41 and 42, so that that the inner peripheries of the toroidal headers 41 and 42 form the minimum diameter gas inlet and outlet openings for the shell chamber.

The unit 39 may be fabricated in the same manner discussed with respect to the unit 1 by first providing the welded connections 53 between the tubes and the inner surfaces of the header half-sections after which the other header half-sections may be welded to the tube-connected half-sections to complete the formation of the headers 41' and 42. In assembling the headers 41 and '42 to the shell, angular brackets 54 may be utilized to maintain the headers properly located. Also, support feet '55 may be connected to the shell 40 as shown in FIGS. 4 and 5.

The improved heat exchanger, as illustrated and described in connection with the various embodiments disclosed, is small and compact, and may be light in weight with maximum strength. By being formed of stainless steel or other corrosion and heat resistant materials it resists attack from the high-temperature heating gases and is adapted for withstanding extreme thermal shock with: out damage.

Further, the improved construction permits the flow of a large volume of high-temperature gases with a minimum pressure loss because of the straight-through flow of the gases in a direct and generally unidirectional path without angular turns in the path of gas flow. Likewise, pressure loss is minimized by the minimum obstruction to gas flow from the tubes through which the medium to be heated flows.

Also, the improved construction provides a maximum of tube surface within a small shell volume along with a minimum obstruction to gas flow incident to the tube connections with the headers. The header inlet and outlet connections extend wholly outside the path of gas flow, and the gas inlet and outlet members, in being connected directly to and axially of the headers enable the inside peripheries of the toroidal headers to serve as the effective inlet and outlet openings for the shell chamber.

Furthermore, the improved construction may be manufactured with a minimum of difliculty as a self-contained unit, and the various welded joints may be formed effectively in a fluid-tight manner by welding. The welded connections may all be readily inspected so that desired safety standards may be satisfied.

Finally, the improved heat exchanger can be adapted for compartmentized construction as in FIG. 2 for separately and simultaneously heating two diflerent liquids or fluids in the same shell by the same counterflow heating gases.

Accordingly, the present invention provides a new heat exchanger construction for heating low-temperature fluids or liquids with relatively high-temperature gases capable of withstanding the thermal shock to which the heat exchanger unit may be subjected without damage, which is strong and light in weight, and which accomplishes the 7 indicated-results and overcomes di-fiiculties unsatisfied .by prior art constructions.

In the foregoing description certain terms have been used for brevity, clearness andunderstanding; but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such terms are utilized for descriptive punposes herein and not for the purpose of limitation and are intended to be broadly construed.

Moreover, the description of the improvements is by way of example, and the scope of the present invention is not limited to the exact details illustrated or to the specific embodiments shown. Thus, although welded joints have been indicated, brazed joints may sometimes be used.

Having now described the features, discoveries and principles of the invention, the construction, operation and use of several embodiments thereof, and the advantageous, new and useful results obtained thereby; the new and useful structures, combinations, arrangements, subcombinations, par-ts and elements which comprise the invention, and mechanical equivalents obvious to those skilled in the art, are set forth in the appended claims.

I claim:

1. In unitary heat exchanger construction, a tubular sheet metal shell, spaced toroidal sheet metal headers circumferentially connected to the interior of the shell at opposite ends thereof and defining therewith a shell chamber, the axes of the headers coinciding with the longitudinal axis of the shell and the outer peripheries of the headers being located in the same cylindrical plane, axially-extending tubular inlet and outlet members for the shell connected respectively with said spaced headers, the inner peripheries of the toroidal headers defining unobstructed inlet and outlet openings for the shell chamber, a plurality of coiled tubes connected to and extending between said spaced headers and located in nested arrangement within the shell chamber with the axes of the tube coils extending parallel to the longitudinal axis of the shell, and tube fluid inlet and outlet means connected respectively to the spaced headers and extending externally of the shell, said toroidal headers and tubes forming a supporting frame for the tubular shell and the tubular inlet and outlet members.

2. In unitary heat exchanger construction, a tubular sheet metal shell, spaced toroidal sheet metal headers circum-ferentially joined to the interior of the shell at opposite ends thereof, the headers being located within the interior of the shell and defining therewith a shell chamber, there being a welded circumferentially-extending joint between each header and the interior of the tubular shell, the axes of the headers coinciding with the longitudinal axis of the shell and the outer peripheries of the headers being located in the same cylindrical plane, axially-extending tubular inlet and outlet members for the shell circumferentially joined respectively to said spaced headers,

the tubularinlet and outlet members and the inner peripheries of the toroidal headers definin g nnobstructed inlet and outletlpassages for the shell chamber, a plurality of coiled tubes connected to and extending between the spaced headers and located in nested arrangement within the shell chamber with the axes of the tube coils extending parallel to the longitudinal axis of the shell, the tube fluid inlet and outlet means connected respectively to the spaced headers and extending externally of the shell, said toroidal headers and tubes forming a supporting frame for the tubular shell and the tubular inlet and outlet members.

3. In unitary heat exchanger construction, a tubular sheet metal shell, spaced toroidal sheet metal headers circumferentially connected to the interior of the shell at opposite ends thereof and defining therewith a shell chamber, the axes of the headers coinciding with the longitudinal axis of the shell and the outer peripheries of the headers being located in the same cylindrical plane, axially-extending tubular inlet and outlet members for the shell connected respectively with said spaced headers defining with the inner peripheries of the headers an unobstructed inlet and an unobstructed outlet for the shell chamber, a plurality of coiled tubes connected to and extending between the spaced headers and located in nested arrangement within the shell chamber with the axes of the tube coils extending parallel to the longitudinal axis of theshell, tube fluid inlet and outlet means connected respectively to the spaced headers and extending externally of the shell, and the coiled tubes having end portions welded to the spaced headers interiorly of the headers, said toroidal headers and tubes forming a supporting frame for the tubular shell and the tubular inlet and outlet members.

4. The heat exchanger construction defined in claim 3 in which each header is formed of two half-sections circumferent-ially welded together at the inner and outer peripheries of the half-sections.

5. The heat exchanger construction defined in claim 3 in which at least two pairs of spaced headers are connected to the shell circumferentially within the ends of the shell, and in which one series of coiled tubes is connected at the ends of its tubes with one pair of spaced headers, and a second series of coiled tubes is connected at the ends of its tubes with another pair of spaced headers.

6. The heat exchanger construction defined in claim I, in which the axially extending tubular inlet and outlet members for the shell have a minimum inside diameter greater than the inner peripheries of the toroidal headers.

References Cited in the file of this patent UNITED STATES PATENTS 1,884,778 Lucke et al. Oct. 25, 1932 2,602,644 Sandstrom July 8, 1952 2,693,346 Peterson Nov. 2, 1954 2,699,322 Feldstein Jan. 11, 1955 

